SOLUTION: a car travels 20 km/h faster than a truck. The car covers 360 km in 3 hours less time than the truck. Find the speed of the truck. (Show your solution)

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Question 389844: a car travels 20 km/h faster than a truck. The car covers 360 km in 3 hours less time than the truck. Find the speed of the truck. (Show your solution)
Found 2 solutions by mananth, ewatrrr:
Answer by mananth(16946) (Show Source):
You can put this solution on YOUR website!
a car travels 20 km/h faster than a truck. The car covers 360 km in 3 hours less time than the truck. Find the speed of the truck. (Show your solution)
...
speed of truck = x km/h
car speed = x+20 km/h
..
time truck = 360/x
time car = 360/(x+20)
..
time truck - time car = 3 hours
360/x-360/(x+20)=3
LCD= x(x+20)
(360(x+20)-360x)/(x(x+20)=3
360x+7200-360x=3x(x+20)
7200=3x^2+60x
3x^2+60x-7200=0
/3
x^2+20x-2400=0
x^2+60x-40x-2400=0
x(x+60)-40(x+60)=0
(x-40)(x+60)=0
x= 40 km/h the speed of truck
...
m.ananth@hotmail.ca

Answer by ewatrrr(24785) (Show Source):
You can put this solution on YOUR website!

Hi,
Let r and t represent the speed and time for the truck
Write as we Read*** D = r*t for the truck and car
r*t = 360km r = 360km/t
(r+20kmph)(t-3hr) = 360km substituting for r so as to solve for t
(360/t + 20)(t-3) = 360km

360t + 20t^2 -3*360 -60t = 360t
20t^2 -60t - 3*360 = 0
t^2 -3t - 54 = 0
factoring
(t-9)(t+6) = 0 tossing out negative solution
t = 9hr r = 40kmph for the truck
CHECKING our Answer for car:
60kmph*6hr = 360km